1. Field of the Invention
The present invention relates to a roll for a mill having a ring of such a wear-resistant material as cemented carbide, ceramics and hard alloy mounted on a roll shaft.
2. Prior Art
As shown in FIG. 1 of the accompanying drawings, a conventional roll for a mill comprises a roll shaft 100, a tapered tubular sleeve 102, a ring 104 and a nut 106. The roll shaft 100 has a tapered portion 100a disposed intermediate opposite ends thereof, a flange portion 100b disposed adjacent to one end of the tapered portion 100a and an externally threaded portion 100c disposed adjacent to the other end of the tapered portion 100a. The ring 104 is disposed around the tapered portion 100a of the roll shaft 100, and the tapered sleeve 102 is press-fitted between the tapered portion 100a and the ring 104 to fix the ring 104 relative to the roll shaft 100 for rotation therewith. The nut 106 is threaded onto the threaded portion 100c of the roll shaft 100 so as to cooperate with the flange portion 100b to retain the sleeve 102 and the ring 104 in place.
The roll described above, however, possesses the drawbacks of requiring a great force for press-fitting the tapered sleeve 102 in place and for detaching it. As a result, it is not easy to mount and detach the sleeve 102, and besides the sleeve 102 has been susceptible to damage or wear. In addition, it has been difficult to obtain a sufficient and uniform clamping force with which the ring 104 is retained in place on the roll shaft 100 for rotation therewith.
In order to circumvent the above problems, a roll as shown in FIG. 2 has been conventionally developed. The roll comprises a roll shaft 110, a pair of collars 112 and 112, a ring 114 and a nut 116. The roll shaft 110, similarly to the roll shaft 100 described above, includes a tapered portion 110a, a flange portion 110b and an exteriorly threaded portion 110c. The roll shaft 100 further includes a spiral groove 118 formed in an outer peripheral surface of the tapered portion 110a and a passageway 120 formed therethrough so as to be communicated at its one end with the groove 118 and to open at its other end to an end face of the roll shaft 110. The ring 114 is press-fitted on the tapered portion 110a intermediate opposite ends thereof. The collars 112 and 112 are fitted on the tapered portion 110a at its opposite ends, respectively, so as to retain the ring 114 therebetween. The nut 116 is threaded onto the threaded portion 110c to cooperate with the flange portion 110b of the roll shaft 110 to firmly retain the ring 114 and the collars 112 in place. In such a roll, the ring 114 can be easily detached from the roll shaft 110 by causing pressurized oil to flow through the passageway 120 into the groove 118 to reduce the friction between the ring 114 and the roll shaft 110. The conventional roll, however, has a drawback that, when stress is concentrated in the roll shaft 110, the roll shaft 110 might be damaged since it includes the groove 118 and the passageway 120.